1. Field of the Invention
The present invention relates to current supply means for a laser flash lamp which is connected to a constant voltage source with a charging capacitor and provides current pulses of a certain duration and amplitude.
2. Description of the Prior Art
The intensity of the flashes produced by the laser flash lamp of a laser device depends on the power of the pulses produced for operating the laser flash lamp. The energy of the pulses is determined by their power (amplitude) and duration.
Pulses of a certain shape are necessary or particularly favorable for certain applications.
Using the pulse shaper circuit one can not only vary the pulse duration but also vary the characteristic of the amplitude of the individual pulses. Known current supply means have in common that the pulses finally provided to the laser flash lamp each have a smooth amplitude characteristic, this characteristic being ramp-shaped for example.
In the prior art three pulse shapes are known:
a) discharging capacitor 1 via switch 3 results in a smooth, sloping pulse FIGS. 1a and 1d)
b) discharging capacitor 1 via switch 3 and a filter (inductive resistor L) results in a smooth, approximately rectangular pulse FIGS. 1b and 1e
c) discharging capacitor 1 via high-frequency switch 4 with pulse width modulation and subsequent low-pass filter L, C results in a smooth pulse whose shape can be adjusted, e.g. ascending (FIGS. 1c and 1e). Such an assembly is described in EP-B1-5595.
In many cases of application the intensity of the flashes emitted by the laser flash lamp plays a considerable part, and the amplitudes of the pulses fed to the laser flash lamp must thus meet corresponding requirements.
For welding, cutting and drilling metal, for example, the power in the individual pulses must exceed a certain threshold value so that the material to be welded is actually melted in the required way. These threshold values are dependent on the material, among other things. This can cause difficulties since the threshold value must be exceeded by the instantaneous pulse power, on the one hand, while a relatively low mean power of the pulse might be required, on the other hand, because the melting of the material necessary for the cutting or welding process is to be limited to a narrow area.